X-ray computer tomography (CT) allows destruction-free and contactless investigation of the inner structure of an object. It is used both in the medical area for investigating the human body and also in the industrial area for quality checking. An important step in X-ray computer tomography is the standardization of the intensity of the X-ray radiation, which is measured behind the object to be investigated by means of an X-ray detector. This generally takes place in such a way that a grey-scale value is determined in the detector, which is interpreted as the reference value for the unattenuated primary X-ray radiation. Using this reference value, the grey-scale values resulting from the X-ray radiation attenuated by the object are standardized.
When using integrating, non-energy-dissipating X-ray detectors, as is conventional in destruction-free checking of objects in the industrial area, there is no possibility for deciding whether the photons impinging on the X-ray detector are to be assigned to the primary X-ray radiation or the secondary X-ray radiation. The photons of the primary X-ray radiation arrived, without interacting in the object to be investigated with said object, from the X-ray source to the X-ray detector, whereas the photons of the secondary X-ray radiation were produced in a scattering process in the object. The measurement of the intensity attenuated by the object by means of the X-ray detector therefore also contains—in addition to the fluorescent radiation induced in the object—a contribution of the randomly scattered photons, in other words a contribution of the secondary X-ray radiation. The secondary X-ray radiation is also designated scattered radiation. The scattered radiation falsifies the measurement of the attenuated primary X-ray radiation, so the image quality of reconstructed images of the object is impaired.